Registry Review Digital Imaging Considerations (Image Production and Evaluation)

Why Digitize? DUH – to make images better! Image enhancement: improve contours and shapes-contrast enhancement, edge enhancement, spatial and frequency filtering, image combining and noise reduction

Image restoration Improve the quality of the images: uses filters and other enhancements to make viewing the image better

Image analysis Measurements and statistics performed on the images: image “processing” image segmentation, feature extraction and classification of objects – Isolate and highlight the objects of interest and classify into specific categories (3-D image formation)

Image Compression Just like “WINZIP” compresses files/images so they can be transmitted and also decrease the storage amount

Image Synthesis Creates images from other images or “non-image data” esp. for CT and MRI and 3-D imaging

Image Processing Point Operations: input image pixel is mapped. Algorithms enable the input matrix to be scanned pixel by pixel until the whole image is “transformed” – sometimes called “gray-level mapping” via using a “look up table” (LUT) – plots the input and output GRAY levels. Modifies the “histogram” of pixel values.

Histogram Indicate the overall BRIGHTNESS and CONTRAST of the image via: –Histogram modification –Histogram stretching

Spatial Frequency Filtering Also called high Pass Filtering – sharpens the image in the spatial domain that seems blurred – uses algorithm that converts the image to spatial frequencies that can be filtered and concentrates on the BEST spatial frequencies which makes a better image!

Spatial Frequency Filtering Low pass filtering – “smoothing process” to reduce noise

Computed Radiography (CR) PSL- photostimulable luminescence PSP- photostimulable phosphor SPS – storage phosphor screen IP- imaging plate SP- storage phosphor PMT – photomultiplier tube PD - photodiode

PSP’s (photostimulable phosphor) is where the latent image is stored – sometimes called “storage phosphor screens (SPSs). Thse are encased in the cassette – sometimes called the IMAGING PLATE

Laser reading of the image A “stimulating laser” reads/converts the latent image to electrons AND erases the latent image from the IP/PSPs –Powder vs “needle” PSPs

Review Chapters 24, 25, 26 ON the UNLV Radiography Program website (under “Pales” then 254) for the computed/digital PowerPoint slides!